The present invention relates to a sprayable, film-forming preparation, for the systemic administration of biologically active substances to plant organisms.
Active substance formulations normally used for plants are emulsion concentrates, suspension concentrates, or so-called wettable powders which are applied by means of different sprayers, spargers, or nebulizing devices (e.g. spray bottles). However, these conventional preparations entail the disadvantage that active substance losses occurring during their application contribute to the contamination of the environmental sections (air, earth, water). This problem is caused by the spray flowing or dripping down the plant surfaces, by rain water washing the spray off, and by the spray drift during application. Their insufficient retention (adherence) and the poor wettability of plant surfaces are further disadvantages of these active substance formulations. These deficiencies frequently interfere with achieving the desired effect.
In the past, many attempts were made to minimize these drawbacks in order to optimize the use of spray agents. According to the art, these attempts can be summarized as follows:
1. Application properties of sprays are improved by adding different substances, such as surface-active agents, substances to prevent drying up, re-humidifying agents, hygroscopic additives, foamers, and in particular adhesion promoters. PA1 2. Selective positioning to plant surfaces is considerably facilitated by loading the spray electrostatically. PA1 3. The retention and wetting properties can be improved by modifying the size of droplets, the spraying pressure, and the spraying distance. PA1 a) 1.0 to 10.0%-wt. of solids, the solids comprising: PA1 b) 0.5 to 80%-wt. of at least one volatile organic solvent PA1 c) 0.5 to 80%-wt. of at least one liquefied gas propellant.
However, none of these measures provide a satisfactory solution with respect to spray drift and environmental impact.
In order to overcome this disadvantage, improved active substance release systems were developed which represent an alternative to conventional sprays. These are depot formulations in the form of flat-shaped, patch-like, adherent or pressure-sensitive adhesive systems which are applied to the plant's shoot axis. These administration forms for active substances effectively overcome the problem of active substance losses and the resulting environmental pollution; however, their use involves a lot of other problems mainly caused by their application. With this kind of device it is extremely important to dimension the size of the contact surface to the plant such that the device does not project past any part of the plant. In case of plants, the growth of which limits the choices of application site, e.g. those completely covering the soil, the application of a device is very difficult. Also, the application of these systems to plants whose surfaces have spines or thorns must be regarded as critical.
In addition, there are problems with respect to using these systems in plants excessively growing in thickness; if the carrier foil is insufficiently stretchable, the application around the stems involves the risk that the plant becomes strangled or that the system grows into the shoot axis, this may damage the underlying tissue layers.
Finally, the use of such systems takes a relatively great deal of time and work not only with respect to the application, but also afterwards since they must be removed when the treatment is completed. Moreover, there is the cost-increasing problem of waste disposal.
According to the state of the art one can say in general terms that there has been considerable progress with respect to the reduction of the required active substance expenditure, the frequency of application, and the undesired effects on other organisms, but that this is accomplished at the expense of other properties.
Film-forming formulations represent another kind of active substance release systems. These are known in the art from the following patents SU 1364267, DE 2804563, and U.S. Pat. No. 4,923,698.
The publication SU 1364267 relates to a film-forming formulation based on carboxymethylcellulose and is used in the storage of agricultural products, in particular in the preservation of fruits and vegetables. To this end, the crop product to be stored is treated by spraying or dipping to form a thin film on the surface of the plant organs; owing to its physical properties, this film protects the plants from unnecessary losses of water and therefore improves their storage life. However, there is no indication in this publication that this preparation contains active substances.
German patent DE 2804563 discloses an active substance-containing, film-forming preparation. It describes a formulation that comprises bird repellents and is used as an agent against bud feeding in useful and flowering shrubs. This is an aqueous polymer dispersion that is stirred into water together with the active substance during the preparation of the plant spray; but it can also be formulated as an active substance-containing wettable powder.
In both, cases the incorporated base polymers, such as homopolymers and copolymers of vinyl acetate or acrylic ester, serve as adhesives.
It is also known in the art to prepare an substance-containing, film-forming formulation, which is a preparation of rodent repellents based on an inorganic active substance absorber (e.g., kaolin, talc). The addition of polymeric adhesion promoters such as methyl or carboxymethylcellulose, polyvinyl alcohol, or urea, results in the formation of a water-insoluble film layer adhering to the plants' surfaces and provides protection against rodents owing to its content of repellents.
U.S. Pat. No. 4,923,698 relates to film-forming, nonpolymeric preparations of insecticides or insect repellents. In this case, a formulation based on a water-in-oil emulsion is proposed which comprises lubricants in addition to the bioactive substances. The lubricants ensure that the film formed by evaporation of a predominant portion of the oil and water phase has a property of rendering the movement of running insects on its surface impossible. In addition, the active substances contained in the film can considerably increase the outcome of pest control because of its direct influence on pests.
In connection with film-forming, sprayable active substance preparations it is finally referred to the articles in the technical journals Hort science (20,50:879-881) and Plant Disease (67:212-214), which describe the experimental use of such developments in plants to control leaf diseases.
These known active substance-containing sprayable formulations, which are capable of forming films, have the severe disadvantage that the films resulting after their application cover the plant surface only for a relatively short time; this is to be ascribed to their hydrophilic character. These formulations are not suitable for the systemic release of active substances to the plant organism because they lack the capability of adhering permanently. The active substances must be present on the plant surface for a sufficiently long time in order to supply the plant organism with the active substance in a concentration sufficient to develop persistent systemic action.
Moreover, it is not the main function of these formulations to administer active substances to the plant, but to provide an external protection of the plant against pests. For this reason, the known application systems do not offer a satisfactory solution of the above-mentioned problem with respect to the administration of biologically active substances to plant organisms.
Thus, the horticultural community wish for ecologically beneficial active substance depot preparations for plants, which are easy to handle, is still left open by the art.